<HTML><HEAD><TITLE>>>(+Number1, +Number2, -Result)</TITLE>
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<H1>>>(+Number1, +Number2, -Result)</H1>
Shifts Number1 right arithmetically by Number2 bits and unifies the
resulting value with Result.


<DL>
<DT><EM>Number1</EM></DT>
<DD>Integer.
</DD>
<DT><EM>Number2</EM></DT>
<DD>Integer.
</DD>
<DT><EM>Result</EM></DT>
<DD>A variable or integer.
</DD>
</DL>
<H2>Description</H2>
   This predicate is used by the ECLiPSe compiler to expand evaluable
   arithmetic expressions.  So the call to &gt;&gt;(Number1, Number2, Result) is
   equivalent to
<PRE>
    Result is Number1 &gt;&gt; Number2
</PRE>
    which should be preferred for portability.
<P>
   The shift behaves as an arithmetic (signed) shift operating on an unlimited
   length two's complement representation.  Shifting by a negative amount is
   the same as shifting by the same positive amount in the other direction.
<P>
   In coroutining mode, if Number1 or Number2 are uninstantiated, the call
   to &gt;&gt;/3 is delayed until these variables are instantiated.

<P>

<H3>Modes and Determinism</H3><UL>
<LI>>>(+, +, -) is det
</UL>
<H3>Exceptions</H3>
<DL>
<DT><EM>(4) instantiation fault </EM>
<DD>Number1 or Number2 is not instantiated (non-coroutining mode    only).
<DT><EM>(5) type error </EM>
<DD>Number1 or Number2 is a number but not an integer.
<DT><EM>(24) number expected </EM>
<DD>Number1 or Number2 is not of a numeric type.
</DL>
<H2>Examples</H2>
<PRE>
Success:
      &gt;&gt;(8, 3, 1).
      &gt;&gt;(17, 3, X).          (gives X = 2)
Fail:
      &gt;&gt;(1, 2, 3).
      &gt;&gt;(16, 2.0, 4.0).
      &gt;&gt;(5, 2, r).
Error:
      &gt;&gt;(A, 2, 6).              (Error 4).
      &gt;&gt;(4 + 12, 2, 4).         (Error 24).



</PRE>
<H2>See Also</H2>
<A HREF="../../kernel/arithmetic/is-2.html">is / 2</A>
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